According to a conventional solar photovoltaic device, which has been used so as to efficiently utilize solar energy, solar panels are generally spread all over a plane facing the sun. Such solar panels are each configured, in general, with the use of an opaque semiconductor. Therefore, such solar panels cannot be stacked when the solar panels are used. On this account, it is necessary to employ large solar panels in order to sufficiently collect sunlight, and accordingly, an installation area of the solar panels becomes larger. Patent Literature 1 discloses, as an example of such a solar photovoltaic device, a technique in which a fluorescent material film is provided on a light-receiving surface of a solar cell module so as to increase energy efficiency of incoming sunlight.
Patent Literature 2 discloses a technique to efficiently utilize solar energy while achieving a reduction of an area of a solar panel. In the technique disclosed in Patent Literature 2, (i) a solar cell is adhered to a side face, which is perpendicular to a daylight surface, of a light absorbing/emitting plate in which a fluorescent substance is dispersed, and (ii) the light absorbing/emitting plate is used as a windowpane of a building. According to the configuration, sunlight, which has entered through the daylight surface, is guided in the light absorbing/emitting plate, and is then converged onto the solar cell.
Patent Literature 3 discloses a technique to efficiently recover solar energy. According to the technique, a solar energy recovering window, in which a solar cell is provided on an edge part of a glass substrate on which a silicon dioxide thin film containing fluorescence is deposited by a liquid phase deposition, is used in a building, an automobile, or the like.